Rotary drum furnace

ABSTRACT

A drum-shaped casing has spaced axial ends provided with inlets and outlets, respectively, and is rotatable about a longitudinal axis which intersects both of these ends. A lining in the interior of the casing is composed of a plurality of axially arrayed annuli of refractory material each of which has a general plane inclined to the longitudinal axis of rotation. Between consecutive annuli radially inward steps are provided which extend circumferentially over most of the circumference of the lining and each of which is bounded by at least two circumferentially extending axially consecutive surface portions which are mutually inclined.

0 United States Patent 1 1 1 3,736,887

Wiedermann 1 June 5, 1973 54 ROTARY DRUM FURNACE 3,404,643 10/1968 Ankerson 1 10 14 [76] Inventor: Wolfgang wiedermann, mmenweg 1,769,924 7 1930 Jacobus ..110 1 A 19, Horst Post Maschehi FOREIGN PATENTS OR APPLICATIONS many 1,270,728 6 1968 G ..110 14 22 Filed: May 5,1971 I many I [2]] Appl. No; 141,061 Primary Examiner-William F. ODea Assistant ExaminerJames C. Yeung [30] Foreign Application Priority Data Att0meyMlchael Smker May 6, 1970 Germany ..P 20 22 126.5 [57] ABSTRACT Aug. 5, 1970 Germany ..P 20 38 896.9 A drum-shaped casing has Spaced axial ends provided [52] U 8 Cl 110/8 R 110/] A 110/14 with inlets and outlets, respectively, and is rotatable 51 IritICL:iiiiiiiiiiiiiiiiiii: ..i ..F2 3g 3/00 about a ioiigiwdihai axis which intersects of [58] Field of Search ..110/8 R, 14, 13, these ends- A iiiiihg the imeiioi of the casing is 110/15, 35, 36, 1 A, 99 R; 263/33 R 46 composed of a plurality of axially arrayed annuli of refractory material each of which has a general plane [56] References Cited inclined to the longitudinal axis of rotation. Between consecutive annuli radially inward steps are provided UNITED STATES PATENTS which extend circumferentially over most of the cir- 2 084 713 6/1937 Thayer ..263/33 R ciimfeieiice 0f the iiiiihg and each of which is 230,141 1/1941 Heuer 2 3 R bounded by at least two circumferentially extending 3,513,788 5/1970 Ostrin ..110/14 axially consecutive surface portions which are mu- 2,068,863 1/1937 Mannshardt..... ...110/l A tually inclined. 1,596,695 8/1926 Stevens .,1 10/1 A 3,346,248 10/1967 Martinet et al. ..263/33 R 12 Claims, 11 Drawing Figures PATENTEDJUM 5 1975 SHEET 1 OF 7 7 l .i/I/I/I/ human Mm A 1 A v mi k PATENTEDJUH 5 1915 3,736. 88 7 SHEET 30F 7 ROTARY DRUM FURNACE BACKGROUND OF THE INVENTION The present invention relates generally to furnaces, and more particularly to an improved rotary drum furnace which is especially but not exclusivelysuitable for use in combusting refuse, waste and similar matter.

The prior art already knows rotary drum furnaces in which the furnace is of drum-shaped configuration and rotated about the longitudinal axis of the drum. The drum itself is composed, essentially, of an outer shell and an inner lining of refractory material. The inner lining, in turn, is composed of a plurality of constituent components which are connected by tongue and groove connectors.

In such a furnace the material to be processed and hereafter this will be explained on hand of the combustion of refuse, waste and the like in such a furnaceis introduced in an inlet provided at one end. In order to make the operation continuous the waste products -ashes and the like should continuously issue from the other end of the drum of the furnace. This is achieved in the prior art by inclining the axis of rotation of the furnace in the direction from the inlet end to the outlet end so that during the rotation the material which enters at the inlet end and is subjected to combustion therein, will advance towards the outlet end and will issue from the latter as ashes or other residue.

According to another prior-art construction the drum is mounted for rotation about an axis which is not inclined to the horizontal, but instead is strictly horizontally oriented itself. In this case the inner surface of the lining is configurated with one or more convoluted channels which during rotation of the drum advance the material from the inlet and to the outlet end.

Irrespective of the construction of such drum furnaces it is necessary that the material introduced into them particularly if it is to be combusted have a certain minimum dwell time therein. This means that the material must not pass through the rotary drum furnace too quickly since otherwise it may issue from the outlet end only partially combusted, which is not satisfactory. On the other hand neither a variation in the inclination of the axis of rotation nor a variation in the convolution of the channels provided on the inner surface of the lining has been found to suffice for obtaining movement of the material at sufficiently slow speed to assure complete combustion, but without remaining stationary insofar as its axial advancement is concerned. To satisfy this requirement it is known from the prior art to provide the inner surface of the lining with radially inwardly extending steps which tend to delay movement of the material from the inlet end of the drum to the outlet end thereof. The lining conventionally is composed of a plurality of axially arrayed annuli of refractory material, and the steps are provided at the junction of consecutive ones of the annuli and extend over the largest part of the circumference of the inner surface of the lining. In other words, the steps are absent at one or more relatively small portions of the inner circumference at each juncture of two consecutive annuli, the purpose being to permit the waste to move from the respectively upstream annulus into the next-following downstream annulus at such locations and without hindrance. In the prior art these steps are defined by vertical edge faces of the respective annuli, that is by edge faces which extend normal or almost normal to the axis of rotation of the drum and which terminate at a sharp radial inward edge.

It is this edge which, as experience has shown, gives riseto difficulties in the aforementioned prior-art constructions. In particular, the movement of the waste over this edge subjects the latter to very substantial wear. This is especially true if the waste or refuse to be combusted contains metallic parts, wires, nails, pieces of glass, rocks or the like, a circumstance which can almost never be precluded without expensive and therefore non-economical prescreening of the refuse. While this wearing-away of the steps at these aforementioned edges may not at first sight appear to be significant, it is pointed out that over a period of time the wear proceeds to such an extent that the movement of the refuse over the steps in axial direction of the drum becomes less and less hampered so that the refuse can move through the drum faster and faster with a concomitant reduction of its dwell time and a decrease in the efficiency of combustion.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the aforementioned difficulties.

Particularly it is an object of the present invention to provide an improved rotary drum furnace in which these problems are avoided.

Still more particularly it is an object of the present invention to provide such an improved rotary drum furnace in which wearing of the lining material at the steps defined by the lining material is substantially reduced and thereby the life expectancy of the lining material significantly increased.

A concomitant object of the invention is to provide such an improved rotary drum furnace in which the material passing through the drum is more efficiently agitated than was known heretofore to prevent it from forming agglomerations and to facilitate its treatment, for instance its combustion.

Still a further object of the invention is to provide such an improved rotary drum furnace in which combustion air is more efficiently and intensively agitated than in the prior-art constructions.

In pursuance of the above objects, and of others which will become apparent hereafter, one feature of the invention recites in a rotary drum furnace, particularly for burning refuse and waste, which comprises a hollow drum-shaped casing having spaced axial ends one of which is provided with an inlet and the other of which is provided with an outlet, and which is rotated about a longitudinal axis intersecting both of these ends. A lining is provided in the interior of the casing and comprises a plurality of axially arrayed annuli of refractory material each of which has a general plane inclined to the longitudinal axis. Furthermore, there is provided a plurality of radially inward steps each defined in the region of the juncture between axially consecutive ones of these annuli, with each of the steps extending circumferentially of the lining over the major portion of the circumference thereof and bounded by at least two circumferentially extending axially consecutive surface portion which are mutually inclined.

The reduction in the wear at the steps of the lining, which is achieved according to the present invention, is the result of providing the steps in such a manner that they are bounded or defined by at least two mutually inclined surface portions which are axially consecutive and extend circumferentially of the drum or lining. The fact that the surface portions are mutually inclined does not means that they must in themselves be planar, because they can also be curved in axial direction as well as in the circumferential direction.

The configuration of the steps in this manner inherently brings with it a better agitation and distribution of the combustion air which is forcibly admitted into the interior of the drum. This can be further improved, however, by admitted the combustion air in such a manner that it is directed into the interior of the drum in a path which is inclined to the axis of the drum and which is tangential with reference to the surface of material accommodated in the drum for treatment, such as combustion.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a somewhat diagrammatic axial section through an embodiment of the present invention;

FIG. 2 is a section taken on line II-II of FIG. 2;

FIG. 3 is a fragmentary detail view, in axial section and on an enlarged scale, illustrating a further embodiment of the invention;

FIG. 4 is a fragmentary diagrammatic detail view illustrating an additional embodiment of the invention;

FIG. 5 is a view of FIG. 4, as seen in the direction of the arrow V in FIG. 4;

FIG. 6 is a fragmentary detail view illustrating a further embodiment of the invention;

FIG. 7 is a view similar to FIG. 6 illustrating another embodiment of the invention;

FIG. 8 is an end-elevational view, in a diagrammatic showing, of an embodiment of the invention;

FIG. 9 is a section taken on line IX-IX of FIG. 8;

FIG. 10 is a section taken on line XX of FIG. 9;

FIG. 11 is a view analogous to FIG. 4 but showing still an additional embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing in detail, and firstly FIGS. 1 and 2 thereof, it will be seen that the illustrated drum furnace has been shown only to the extent necessary for an understanding of the invention. For instance, no fuel supply or the like, no mounting means for mounting the drum for rotation and no drive means for effecting such rotation have been illustrated because these may all be conventional.

Keeping this in mind it is pointed out that the drum of the rotary drum furnace has an outer casing l, for instance of steel. One end of the casing 1 has an inlet for material to be combusted, and the opposite end has an outlet 3 for the residue, such as ashes and the like. The interior of the casing is provided with a lining composed ofa plurality of axially arrayed annuli 4 of refrac' tory material and whose general planes are inclined with reference to the longitudinal axis of rotation of the drum, which is identified with reference numeral 5.

At the juncture between consecutive ones of the annuli 4 there are provided radially inward steps 6 which extend almost over the entire circumference of the lining and whose purpose it is to delay material moving longitudinally of the drum from the inlet 2 towards the outlet 3 thereof. The purpose is to assure as complete as possible and as intense as possible a combustion of this material.

FIG. 2 shows that in the embodiment of FIGS. 1 and 2 the steps 6 are defined by mutually inclined surface portions 7 and 8 which are axially consecutive and which extend circumferentially of the lining. The configuration of these steps advantageously influences the life expectancy of the annuli 4, because there is now no longer a sharp edge at the radially inner limitation of the respective step 6, due to the provision of the mutually inclined surface portions 7 and 8. At the same time this step configuration provides for intensified and therefore advantageous agitation of combustion air which is admitted into the drum.

A consideration of FIG. 2 clearly shows that along the axially extending lines 6a and at the inner circumference of the lining the steps 6 do not exist. In other words, the radial height of the steps tapers circumferentially to these lines 60 and 7a, respectively, so that in the region of these lines the material can freely pass longitudinally of the rotating drum towards the outlet end 3 thereof. On the other hand, in the regions identified with the arrows A in FIG. 2 the radial height of the steps 6 is at its maximum, and it will be seen that the regions A are spaced through from the lines 6a and 7a, respectively.

Drums in such rotary drum furnaces may of course be of various different sizes. If the drum is of relatively large diameter, then it is advantageous -especially for reasons of assembly and disass'embly to have the annuli be composed of individual sections. Such an embodiment is illustrated in FIG. 3. In that Figure the individual annuli 4, which are only fragmentarily shown, are each composed of three sections 9, 10 and 11 which themselves are axially arrayed and together make up one of the annuli 4. These annuli, as well as the sections 9, l0 and 11, can be connected and maintained in this relationship as illustrated diagrammatically in FIG. 1, by means of axially extending rods or bars or in any other suitable way well known to those skilled in the art and therefore not requiring a discussion because it does not in itself form a part of the present invention.

With respect to the embodiment of FIG. 3, as well as to that of FIGS. 1 and 2 and all subsequent embodiments, it is pointed out that the annuli of refractory material may be of any suitable refractory material, including fire brick, suitable metal, graphite, suitable synthetic plastics or any combination of these materials.

In FIG. 3, as in FIGS. 1 and 2, each step is defined by two mutually inclined surface portions 7 and 8.

In the embodiment of FIGS. 4 and 5 I have illustrated fragmentarily two of the annuli which are here identified with reference numeral 12. In this embodiment the annuli each consist of a carrier portion or support portion 13 and an inner portion 14 which is releasably connected with the carrier portion 13 and faces the interior of the drum furnace, that is the combustion chamber thereof. The combustion chamber is not illustrated in FIGS. 4 and 5 but its location with reference to the section 14 will be readily understood. In the embodiment of FIGS. 4 and 5 the releasable connection between the sections 13 and 14, which of course are each of annular outline, is effected by a dove-tail connection (compare FIG. 5) so that a sliding connection and disconnection is assured. In this embodiment the material of the section 13 need not be of as high quality as that of the section 14 because it is subjected to lesser stresses; thus, the total cost of each of the annuli 12 can be lower than if the annulus were to be made entirely of the material of the section 14.

In FIG. 6, which otherwise illustrates the same embodiment as FIGS. 4 and 5, only the surface portion 7 is planar whereas the surface portion 8 is curved not only in circumferential but also in axial direction.

In FIG. 7 l have illustrated an embodiment in which both surface portions 7 and 8 are curved so that the step 6 is defined and outlined by a continuously curved surface. In other respects the embodiment of FIGS. 6 and 7 may be the same as that of FIGS. 4 and 5.

Coming to the embodiment illustrated in FIGS. 8-10 it will be seen that herein the drum of the rotary drum furnace is identified in toto with reference numeral 18 and is provided at one end, that is its inlet end, with an inlet hopper 19 which is diagrammatically illustrated and through which material to be combusted is admitted to the interior of the drum.

Combustion air is admitted at the same inlet end through a supply channel 20 at least the inner end portion of which (compare FIG. 9) is so inclined with reference to the axis of rotation 5 of the drum 18 that incoming air (identified by the arrows 22) is agitated and swirled by contact with the inner surface 21 of the lining and/or material which is accommodated on this inner surface, which contact takes place tangentially as indicated.

It is clearly shown in FIG. 9 that a portion of the incoming air will contact the surfaces at the steps 6 and will be either reflected or deflected in circumferential direction. The remainder of the air contacts the surface of material accommodated on the inner surface 21 and forms eddys the size and direction of which depends upon the surface configuration of the material being combusted.

Admitting the air in this manner also creates in effect a pneumatic retardation which increases the dwell time of the material which passes from the inlet toward the outlet end of the drum. The good loosening and distribution of the material being combusted, due to the rotation of the drum and to the provision of the projections 17 if such are provided, coupled with the changing direction of air and flames, result in an intensive combustion of the material which makes possible the combustion of all types of waste and refuse which are commonly known. Thus, in addition to household and commercial refuse and waste which is normally found in municipal collections, the apparatus according to the present invention can be utilized for combusting oilcontaining wastes such as oil sludges, residues from oil and gasoline separators, residues from fat separators, residues from the cleaning of oil and other tanks, and oil-containing dirt.

In FIG. 11, finally, there is shown an embodiment where the carrier portions 13 are provided with circumferentially extending ribs 30 of dovetail crosssection, and the inner portions 31 are provided with mating circumferentially extending recesses 32 accommodating the respective ribs. Other components are identified with the same reference numerals designating them in FIG. 4.

It will be appreciated that the configuration of the surface portions bounding the steps, as disclosed herein, not only serves to loosen the refuse and waste material and to prevent or counteract its caking and bunching, but also creates strong eddying of the combustion air which contacts several inclined surface portions and is deflected in different directions. A part of the combustion air is deflected back toward the inlet and subsequently reverses its direction under the influ ence of the suction means (conventional and not illustrated) which communicates with the outlet of the drums. This causes a fluctuating air flow and a fluctuating flame motion.

Also, the inclined surface portions bounding the steps effect air distribution in circumferential direction, and this in turn aids in intensive aeration of the material which is well spread apart due to the inclination of the general planes of the annuli relative to the axis of rotation. All of this enhances the combustion.

The configuration of the steps according to the invention also makes it easier for large objects, such as wire sections, metal pieces and the like, to pass from one annulus into the next.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a rotary drum furnace, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended:

1. In a rotary drum furnace, particularly for burning refuse and waste, in combination, a hollow drumshaped casing having spaced axial ends one of which is provided with an inlet and the other of which is provided with an outlet, and being rotatable about a longitudinal axis intersecting both of said ends; a lining in the interior of said casing and comprising a plurality of axially arrayed annuli of refractory material each having a general plane which is inclined to said longitudinal axis; and a plurality of radially inward steps each defined in the region of the juncture between axially consecutive ones of said annuli, each of said steps extending circumferentially of said lining over the major portion of the circumference thereof and being bounded by at least two circumferentially extending axially consecutive surface portions which are mutually inclined at an obtuse angle and are each provided on one of said axially consecutive annuli.

2. In a furnace as defined in claim 1, wherein said annuli are composed from a refractory material selected from the group including metal, graphite, synthetic plastic, fire clay and combinations thereof.

3. In a furnace as defined in claim I, wherein at least one of said surface portions is curved in longitudinal direction of said axis.

4. In a furnace as defined in claim 1, said annuli each having an inner circumferential surface; and further comprising inwardly extending projections provided on at least some of said inner circumferential surfaces.

5. In a furnace as defined in claim 1, said annuli each being composed of a radially outer annular portion and a radially inner annular portion located within the confines of the respective outer annular portion and releasably connected with the latter.

' 6. In a furnace as defined in claim 5, wherein said radially inner annular portions are composed of a plurality of discrete sections.

7. In a furnace as defined in claim 6, wherein said discrete sections are plate-shaped sections.

8. In a furnace as defined in claim and further comprising a dove-tail connection between each outer annular portion and the associated inner annular portion.

9. In a furnace as defined in claim 8, said dove-tail connection comprising an elongated groove on one and an elongated rib on the other of said annular portions of the respective annulus, and wherein said groove and rib are elongated in direction axially of the respective annulus.

10. In a furnace as defined in claim 8, said dove-tail connection comprising an elongated groove on one and an elongated rib on the other of said annular portions of the respective annulus, and wherein said groove and rib are elongated in direction transversely of the longitudinal axis of the respective annulus.

11. In a furnace as defined in claim 5, wherein said inner annular portions of axially consecutive ones of said annuli overlap one another axially at the juncture between said consecutive annuli.

12. In a furnace as defined in claim 1; and further comprising admitting means for admitting in the region of said one end at least one stream of combustion air in a direction inclined to said longitudinal axis of said casing and tangential to the surface of material admitted into the interior of said lining through said inlet. 

1. In a rotary drum furnace, particularly for burning refuse and waste, in combination, a hollow drum-shaped casing having spaced axial ends one of which is provided with an inlet and the other of which is provided with an outlet, and being rotatable about a longitudinal axis intersecting both of said ends; a lining in the interior of said casing and comprising a plurality of axially arrayed annuli of refractory material each having a general plane which is inclined to said longitudinal axis; and a plurality of radially inward steps each defined in the region of the juncture between axially consecutive ones of said annuli, each of said steps extending circumferentially of said lining over the major portion of the circumference thereof and being bounded by at least two circumferentially extending axially consecutive surface portions which are mutually inclined at an obtuse angle and are each provided on one of said axially consecutive annuli.
 2. In a furnace as defined in claim 1, wherein said annuli are composed from a refractory material selected from the group including metal, graphite, synthetic plastic, fire clay and combinations thereof.
 3. In a furnace as defined in claim 1, wherein at least one of said surface portions is curved in longitudinal direction of said axis.
 4. In a furnace as defined in claim 1, said annuli each having an inner circumferential surface; and further comprising inwardly extending projections provided on at least some of said inner circumferential surfaces.
 5. In a furnace as defined in claim 1, said annuli each being composed of a radially outer annular portion and a radially inner annular portion located within the confines of the respective outer annular portion and releasably connected with the latter.
 6. In a furnace as defined in claim 5, wherein said radially inner annular portions are composed of a plurality of discrete sections.
 7. In a furnace as defined in claim 6, wherein said discrete sections are plate-shaped sections.
 8. In a furnace as defined in claim 5; and further comprising a dove-tail connection between each outer annular portion and the associated inner annular portion.
 9. In a furnace as defined in claim 8, said dove-tail connection comprising an elongated groove on one and an elongated rib on the other of said annular portions of the respective annulus, and wherein said groove and rib are elongated in direction axially of the respective annulus.
 10. In a furnace as defined in claim 8, said dove-tail connection comprising an elongated groove on one and an elongated rib on the other of said annular portions of the respective annulus, and wherein said groove and rib are elongated in direction transversely of the longitudinal axis of the respective annulus.
 11. In a furnace as defined in claim 5, wherein said inner annular portions of axially consecutive ones of said annuli overlap one another axially at the juncture between said consecutive annuli.
 12. In a furnace as defiNed in claim 1; and further comprising admitting means for admitting in the region of said one end at least one stream of combustion air in a direction inclined to said longitudinal axis of said casing and tangential to the surface of material admitted into the interior of said lining through said inlet. 